Protein materials derived from vegetable protein sources such as soybeans are utilized for nutritional purposes in a variety of foods and beverages. Vegetable protein isolates, having a protein content of at least 70%, are particularly useful nutritional supplements in foods and beverages.
The usefulness of such nutritional vegetable protein materials in beverages depends in part of the dispersability or suspendibility of the protein material in the particular type of aqueous medium used in the preparation of the beverage. While such protein materials are generally dipsersible in aqueous media, it has been more difficult to employ these protein materials in conjunction with certain vitamins and minerals that may be required to form a nutritionally complete beverage, such as an infant formula. Fortification of a liquid product with an alkaline earth metal material, particularly calcium, presents a problem since most forms of such materials employed for nutritional supplementation in beverages are relatively insoluble in aqueous media. These materials readily precipitate or settle from an aqueous suspension of a nutritious beverage, particularly when present at relatively high concentrations, thereby giving the beverage a gritty mouthfeel and requiring the consumer of the beverage to shake the beverage relatively often to ensure adequate consumption of the minerals in the beverage.
An effective method for formulating alkaline earth metal mineral fortified protein compositions for use in aqueous media beverages is provided in U.S. Pat. No. 4,642,238. According to this method, a hydrated gel of an alkaline earth metal salt is formed, the gel is added to an aqueous slurry of an isolated vegetable protein material, and the combined gel and protein material are dewatered to provide the alkaline earth mineral fortified protein composition. The alkaline earth metal mineral fortified protein composition provides improved suspension of the mineral in an aqueous medium beverage.
The method of the U.S. Pat. No. 4,642,238 patent allows moderate levels of an alkaline earth metal salt to be incorporated into a vegetable protein composition, but is ineffective or commercially inefficient when relatively high levels of mineral fortification of the protein composition are desired. Formation of a hydrated gel of an alkaline earth metal phosphate salt by the reaction3M(OH)2+2H3PO4→M3(PO4)2+6H2Owhere M is an alkaline earth metal is the most preferable method for forming the hydrated gel since no salt by-product is formed which must be removed from the gel before combining the gel with a protein material. Insoluble alkaline earth metal hydroxide materials do not form a hydrated gel with phosphoric acid when the phosphoric acid is slowly added to a solution of the alkaline earth metal hydroxide, as disclosed in the '238 patent.
The degree to which a protein material can be fortified with a mineral from a hydrated alkaline earth metal phosphate gel is limited by the maximum concentration of the alkaline earth metal in the gel. Unlimited amounts of the gel cannot be added to a slurry of the protein material to obtain a desired level of mineral fortification since the drying process of the combined gel and protein material is adversely affected by a low solids level. Spray drying the combined protein/gel combination is the only effective method of drying to obtain a dried product which has excellent dispersability in an aqueous medium since other drying methods do not uniformly mix the mineral fortifying salt and the protein material. Slurries having less than about 5% solids cannot be effectively spray dried due to the fine particle size produced by spray drying a low-solids slurry, and the resulting loss of product. Prior to the present invention, a hydrated gel formed from an alkaline earth metal hydroxide and phosphoric acid could contain a maximum solids level of about 4.5%. A vegetable protein material slurry could contain about 20% solids. The hydrated gel of 4.5% solids and the vegetable protein slurry of 20% solids are combined together at a ratio to produce a hydrated gel—vegetable protein slurry mixture having a solids content of about 14%. This mixture is spray dried to give a mineral fortified vegetable protein having an alkaline earth metal content of about 3% by weight.